Microwave induced cracks have the potential to enhance metal recovery from coarse sphalerite particles in heap leaching operations by creating new crack surface areas for lixiviant. The characteristics and quantity of microwave induced cracks and how these cracks subsequently affect heap leaching recovery has not yet been investigated. This study characterised and quantified microwave induced crack damage by applying X-ray computed tomography (XCT) and Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN) analysis. Sphalerite ore particles representing small (-5 + 4.75) mm, medium (-16 + 9.5) mm, and large (-25 + 19) mm HPGR and cone crushed products were microwave treated at specific microwave heating energies of between 1 and 3 kW h/t Image segmentation, thresholding and spatial registration techniques were used to study crack patterns in the XCT 3D images. The results showed the presence of microwave induced cracks within the cone and HPGR microwave treated particles. The cracks consist of both interphase trans-granular and grain boundary cracks. Both XCT and QEMSCAN analysis results showed that microwave treatment resulted in a significant increase of over 500% in crack volume for both modes of prior comminution at all particle sizes. (C) 2015 Elsevier Ltd. All rights reserved.